Pipe coupling using shape memory alloy

Abstract

A pipe coupling comprises a cylindrical coupling member fabricated of shape memory alloy and a foil as a metallic member of low melting point attached to an internal surface of the cylindrical coupling member, a melting point of the foil being lower than that of materials of a pipe to be joined to the pipe coupling and of the coupling member. Further, a pipe coupling comprises a cylindrical coupling member fabricated of shape memory alloy, at least two pieces of ring protrusions formed on an internal surface of the cylindrical coupling member, and metallic member of low melting point which is attached to an internal surface of the cylindrical coupling member between the ring protrusions, a melting point of the metallic member of low melting point being lower than that of materials of a pipe to be joined and of the coupling member. Furthermore, a pipe coupling comprises a cylindrical coupling member fabricated of shape memory alloy, a ring stopper formed at a central portion of the cylindrical coupling member in the axial direction thereof, and metallic member of low melting point attached to an internal surface of the cylindrical coupling member both sides of the ring stopper, a melting point of the metallic member of low melting point being lower than that of materials of a pipe to be joined and of the coupling member.

What is claimed is: 
     
       1. A pipe coupling comprising: a cylindrical coupling member made from shape memory alloy;   at least two substantially ring shaped protrusions formed on an internal surface of said cylindrical coupling member; and   a metallic member of low melting point which is attached to an internal surface of said cylindrical coupling member between said ring shaped protrusions, a melting point of said metallic member of low melting point being lower than that of materials of a pipe to be joined and of the coupling member.   
     
     
       2. The pipe coupling of claim 1, wherein said ring shaped protrusions comprise four pieces of ring protrusions positioned symmetrically relative to the center of the coupling member in the axial direction of the cylindrical coupling member. 
     
     
       3. The pipe coupling of claim 1, which further comprises a metallic member of low melting point attached to an internal surface at the ends of the cylindriacl coupling member. 
     
     
       4. The pipe coupling of claim 1, wherein said metallic member of low melting point has at least one slit therein; and a cross section of said metallic member is C-shaped. 
     
     
       5. The pipe coupling of claim 1, wherein said shape memory alloy is a shape memory alloy of stainless steel. 
     
     
       6. The pipe coupling of claim 1, wherein said metallic member of low melting point is a soft solder of Ag-Sn. 
     
     
       7. The pipe coupling of claim 1, wherein said metallic member of low melting point is a soft solder of Ag-Sn-Sb. 
     
     
       8. The pipe coupling of claim 1, wherein: said shape memory alloy is a shape memory alloy of stainless steel;   said metallic member of low melting point has at least one slit in the axial direction thereof, and has a C-shaped section; and   said metallic member of low melting point is a soft solder of Ag-Sn.   
     
     
       9. A pipe coupling comprising: a cylindrical coupling member fabricated of shape memory alloy;   a ring stopper formed at a central portion of said cylindrical coupling member in the axial direction thereof; and   a metallic member of low melting point attached to an internal surface of said cylindrical coupling member on both sides of said ring stopper, a melting point of said metallic member of low melting point being lower than that of meterials of a pipe to be joined and of the coupling member.   
     
     
       10. The pipe coupling of claim 9, wherein said shape memory alloy is a shape memory alloy of stainless steel; 
     
     
       11. The pipe coupling of claim 9, wherein said metallic member of low melting point is a soft solder of Ag-Sn. 
     
     
       12. The pipe coupling of claim 9, wherein said metallic member of low melting point is a soft solder of Ag-Sn-Sb. 
     
     
       13. The pipe coupling of claim 9, wherein: said shape memory alloy is a shape memory alloy of stainless steel; and   said metallic member of low melting point is a soft of Ag-Sn.   
     
     
       14. The pipe coupling of claim 9, wherein said metallic member is foil. 
     
     
       15. The pipe coupling of claim 1, wherein said cylindrical coupling member fabricated of shape memory alloy contracts in the radial direction thereof upon being heated. 
     
     
       16. The pipe coupling of claim 9, wherein said cylindrical coupling member fabricated of shape memory alloy contracts in the radial direction thereof upon being heated.